This invention relates generally to abrasive blasting and more particularly to air filtration systems used in conjunction with abrasive blasting rooms.
Maintaining a clean environment is critical in many industries. Air borne debris has detrimental affects both upon products and workers in the area. This makes the collection of dust and other airborne particles generated from abrasion blasting, removing of dry products, or similar dust generating activities, essential for the well being of workers and the environment. In many industrial areas, the Federal Environmental Protection Agency has set strict standards for the air quality in order to protect workers and the environment.
Within the abrasive blasting industry, the need for clean air is critical since dirty air: (i) obstructs visibility which may lead to damage to the substrate being cleaned and (ii) may require more expensive and cumbersome breathing equipment to protect the operator.
Suspended debris in the abrasive blasting industry consists not only of dust from spent abrasive medium, but also from the removed paints and coatings, many of which are hazardous to an operator's health.
Another important consideration is the portability of equipment. With the increasing need for air filtration at abrasive blast sites such as bridges, exteriors of buildings, dry docked boats, and the like, the need to have a truly portable system is paramount.
In many situations, the paint or coating to be removed must be handled with care since many contain heavy metals such as lead or chrome which results in the residue from these coating being classified as hazardous or toxic waste. Air borne contaminants are no exception. These air borne contaminants must be filtered out before the air is exhausted into the environment.
To provide for a clean working environment, the typical solution is to provide a cyclone wind turbine to draw air, via duct work, from the to-be-cleaned room. This provides a negative pressure room to encourage the debris to stay within the system and not leave the room.
An example of such a system is described by U.S. Pat. No. 4,789,387, entitled "Dust Collector" issued to Nemesi et al. on Dec. 6, 1988.
Typical movement of air within an abrasive blast room is in the 3000-8000 Cubic Feet per Minute (CFM). To achieve this movement and cleaning of the air, motors on the order of one horse or more are required. Motors having this capability use an exorbitant amount of electrical energy and thereby reduces the efficiency of the abrasive blasting system.
Furthermore, these systems are designed for a specific room under standardized conditions. Little flexibility is provided since to increase the CFM capacity of the system requires major redesign and reconstruction of the cyclone, ducts, and bag houses.
To provide for a more efficient use of the electrical energy, and also give a little flexibility, some air cleaning systems utilize wall units. These modular units fit into a wall of the room. Such apparatus are commercially sold by Torit, a division of Donaldson Company, Inc. and are associated with Environmental Control Booths.
The Torit apparatus eliminates the duct work normally associated with dust control and provides for louvers between the to-be-cleaned room and the dust collection apparatus. The dust collection apparatus uses standard air filtration cartridges. Air is drawn directly through the louvers, through the filter cartridges, and then exhausted into the atmosphere.
Although the Torit apparatus does come in three different sizes, modification to accommodate different air flow requirements is cumbersome and often impossible since large air flow requirements would require long banks of units and motors with complex motor start control systems. Further, the Torit apparatus is designed to provide only minimal cleaning capability since only a small portal for air flow is provided. Even more restrictive, the Torit apparatus is not easily made portable.
Without portability, the Torit apparatus is totally unsuitable for many critical applications which arise in the modern world.
It is clear from the foregoing that an efficient, portable, and versatile air cleaning system does not exist.